The purpose of this study is to determine in what manner chronic steroid treatment physiologically alters skeletal muscle, and how this relates to steroid myopathy. There is preliminary evidence to suggest that steroid treatment may affect: resisting membrane permeability, action potential generation, and excitation-contraction coupling. Certain steroids may produce myopathy more readily than others, and certain muscle groups may be particularly susceptible to steroid myopathy. The trim course of development of steroid myopathy is not known. In order to quantify the effect of steroid treatment on muscle sarcolemmal, sarcoplasmic reticulum, and myofibrillar protein function, it will be necessary to serially study the physiologic changes in several different steroids. This will determine whether the physiologic changes depend upon steroid type, muscle fiber type, and muscle location. The physiologic parameters to be studied are: membrane potential, membrane cable parameters, resting membrane chloride and potassium permeabilities, ratio of resting membrane sodium and potassium permeabilities (PNA/PK), sensitivity of voltage-dependent sodium and potassium channels, myofibrillar sensitivity to calcium, sarcoplasmic reticulum calcium uptake and release ability, muscle fiber twitch characteristics, and twitch, tetanic, and maximal calcium activated tension normalized to muscle fiber cross-sectional area.